1. Field of the Invention
The present invention relates to a webbing retractor which, at the time a vehicle rapidly decelerates and by using a locking device, temporarily locks rotation in a webbing pull-out direction of a spool on which a webbing for restraining a vehicle occupant is taken-up in a roll form by urging force, and which, in this state, permits a predetermined amount of rotation of the spool in the webbing pull-out direction due to load of a predetermined value or more being applied from the vehicle occupant to the webbing.
2. Description of the Related Art
Generally, a three-point-type seat belt device is structured so as to include a webbing for restraining a vehicle occupant, an anchor plate, a webbing retractor, a shoulder anchor, a tongue plate, and a buckle device. The anchor plate fixes one end portion of the webbing to the floor of the vehicle. The webbing retractor is a device which is disposed at the lower end portion of the center pillar of the vehicle and which takes-up the other end portion of the webbing in a roll form by urging force. The shoulder anchor is disposed at the upper portion of the center pillar, and an intermediate portion of the webbing is movably inserted through the shoulder anchor. An intermediate portion of the webbing passes through the tongue plate. The buckle device stands upright at the side of a seat of the vehicle, and the tongue plate engages therewith.
Various types of the above-described webbing retractor have been proposed. In one type, when the vehicle rapidly decelerates, the webbing retractor temporarily stops rotation of the spool in the webbing pull-out direction. Thereafter, due to a load of a predetermined value or more being applied to the webbing from the vehicle occupant, a torsion bar, which is provided integrally with and coaxially with the axially central portion of the spool, is twisted. The spool is thereby rotated by a predetermined amount in the webbing pull-out direction. In this way, the load which the vehicle occupant receives from the webbing which is in a locked state can be lessened. This mechanism is called a xe2x80x9cforce limiter mechanismxe2x80x9d.
In a webbing retractor equipped with this type of a force limiter mechanism, a locking assembly, which locks rotation of the torsion bar in the webbing pull-out direction at the time when the vehicle rapidly decelerates, must be coaxially fixed to the axially central portion of the spool shaft. Thus, conventionally, the locking assembly was fixed to the spool by inserting a stopper, which was made of resin and formed in a substantial U shape, into the spool in a direction orthogonal to the axis of the spool, and by plastically deforming the stopper.
In recent years, structures have been proposed in which the load, at the time when the spool can rotate again by a predetermined amount in the webbing pull-out direction due to an increase in the webbing tensile force after the rotation of the spool in the webbing pull-out direction has been stopped at the time when the vehicle rapidly decelerates (this load is the force limiter load and hereinafter will be abbreviated as xe2x80x9cFL loadxe2x80x9d), is set to be two stages. Namely, in the initial stage of the time when the vehicle rapidly decelerates, the FL load is maintained high, and the energy absorption efficiency is high. Thereafter, by reducing the FL load, the load which the vehicle occupant receives from the webbing is reduced.
When the above-described fixing structure is applied to a webbing retractor which is equipped with a force limiter mechanism which is this two-stage FL load type, a large load in the thrusting direction arises. Thus, there is the possibility that the conventional resin stopper will not be able to withstand this load, and the locking assembly will spring out in the axial direction. Accordingly, this springing-out of the locking assembly must be suppressed by forming the stopper of metal. However, if the stopper is formed of metal, press-fitting of the stopper into the spool by plastic deformation is not possible, and therefore, noise arises at the time of ordinary operation of the webbing retractor.
In view of the aforementioned, an object of the present invention is to provide a webbing retractor which can prevent the generation of noise at the time of ordinary operation, which noise is caused by a stopper member being insufficiently pressed-in, and which can more strongly fix a locking device to a spool.
An aspect of the present invention is a webbing retractor comprising: a spool taking up a webbing, for restraining a vehicle occupant, in a roll form by urging force; an energy absorbing member permitting a predetermined amount of rotation of the spool in a webbing pull-out direction; a locking device stopping rotation of the energy absorbing member at a time of rapid deceleration of a vehicle; and a stopper member which, when installed, applies both press-in load in a thrusting direction and press-in load in a radial direction, between one portion of the locking device and the spool. The energy absorbing member is connected coaxially to the spool, and usually rotates integrally with the spool. In a state in which rotation of the energy absorbing member in the webbing pull-out direction is impeded, the energy absorbing member deforms due to a load of a predetermined value or more being applied to the energy absorbing member via the spool, and the energy absorbing member permits a predetermined amount of rotation of the spool in the webbing pull-out direction. One portion of the locking device is inserted coaxially between the energy absorbing member and the spool. The stopper member is a member which is installed by being inserted between the outer peripheral surface of one portion of the locking device and the inner peripheral surface of the spool, from a direction orthogonal to the axis.
In the webbing retractor relating to the present invention, the stopper member may have a terminal end portion which is formed by being bent back and which, in an installed state, applies elastic restoring force in the radial direction between one portion of the locking device and the spool.
In the webbing retractor relating to the present invention, a protruding portion may be formed at the terminal end portion of the stopper member, and the protruding portion protrudes in a widthwise direction of the terminal end portion, and at a time of installation, due to the protruding portion being pushed relatively from a spool side, the protruding portion elastically deforms and applies elastic restoring force in the thrusting direction between one portion of the locking device and the spool.
Further, in the webbing retractor relating to the present invention, a portion of the stopper member which opposes the terminal end portion may, in an installed state, be pressed so as to contact and be trained along the outer peripheral surface of one portion of the locking device.
In the webbing retractor relating to the present invention, a projecting portion, which projects in a direction opposite to the direction in which the terminal end portion is bent back, may be formed at the portion which is pressed into contact in this way. Moreover, an interference portion, which, in the installed state of the stopper member, interferes with the projecting portion and hinders movement of the stopper member in the direction opposite to the direction of insertion, may be formed at the spool.
In the webbing retractor relating to the present invention, in addition to any of the above-described structures, a resistance imparting device may be provided between the spool and the locking device. The resistance imparting device usually rotates integrally with the spool without imparting rotational resistance to the spool. After locking by the locking device, in an initial stage of rotation of the spool in a webbing pull-out direction, the resistance imparting device imparts resistance to the rotation of the spool in the webbing pull-out direction, and thereafter, cancels the state of imparting resistance.
In accordance with the present invention, usually, the energy absorbing member, which is connected coaxially to the spool, rotates integrally with the spool in the webbing pull-out direction and the webbing take-up direction.
When the vehicle rapidly decelerates, rotation of the energy absorbing member in the webbing pull-out direction is stopped by the locking device. In this way, rotation of the spool in the webbing pull-out direction also is temporarily stopped. Inertial force toward the front of the vehicle is applied to the vehicle occupant, and load in the pulling-out direction is applied to the webbing from the vehicle occupant. When this load reaches a predetermined value or more, the energy absorbing member deforms, and the spool is rotated by a predetermined amount in the webbing pull-out direction. Then, the load applied to the vehicle occupant from the webbing is reduced.
Here, in the present invention, the stopper member is, from the direction orthogonal to the axis, inserted into and installed in between the inner peripheral surface of the spool and the outer peripheral surface of one portion of the locking device which is coaxially inserted between the energy absorbing member and the spool. In the state in which the stopper member is installed between the outer peripheral surface of one portion of the locking device and the inner peripheral surface of the spool, not only press-in load in the thrusting direction, but also press-in load in the radial direction, is applied between the two. Thus, sufficient press-in load is applied between the two, and insufficient pressing-in of the stopper member is eliminated.
Moreover, in addition to the press-in load in the thrusting direction, press-in load in the radial direction is also applied. Therefore, the locking device can be even more reliably fixed to the spool.
In accordance with the present invention, there are cases in which the stopper member is provided with a terminal end portion which is formed by being bent back. In this case, when the stopper member is installed in, the terminal end portion elastically deforms and applies elastic restoring force in the radial direction between the spool and one portion of the locking device. Accordingly, elastic restoring force in the radial direction can be applied between the two by the simple structure of bending back.
In accordance with the present invention, there are cases in which a protruding portion, which protrudes in the widthwise direction of the terminal end portion, is provided at the terminal end portion of the stopper member. In this case, when the stopper member is installed, the protruding portion is relatively pushed from the spool side and the terminal end portion elastically deforms in the widthwise direction thereof, i.e., in the thrusting direction. Thus, elastic restoring force in the thrusting direction is applied between the spool and one portion of the locking device. Accordingly, the press-in load in the thrusting direction can be increased as compared with a structure in which no protruding portion is provided. Moreover, because the protruding portion can be formed integrally with the terminal end portion of the stopper member, the provision of the protruding portion does not lead to an increase in the number of parts.
In accordance with the present invention, there are cases in which, in the state in which the stopper member is installed, the portion of the stopper member, which portion opposes the terminal end portion, is pressed so as to contact and be trained along the outer peripheral surface of one portion of the locking device. In this case, the surface area of contact between the stopper member and the one portion of the locking device increases. Accordingly, both the press-in load in the thrusting direction and the press-in load in the radial direction can be increased simultaneously.
In accordance with the present invention, there are cases in which, when the stopper member is inserted, from the direction orthogonal to the axis, between the inner peripheral surface of the spool and the outer peripheral surface of one portion of the locking device, the portion of the stopper member which opposes the terminal end portion is pressed so as to contact and be trained along the outer peripheral surface of the one portion of the locking device. When, accompanying this, the projecting portion, which is formed at the portion of the stopper member which opposes the terminal end portion, similarly is inserted in and the stopper member reaches the installed state (i.e., when the amount of insertion of the stopper member reaches the amount corresponding to completion of installation), the projecting portion interferes with the interfering portion formed at the spool. In this way, movement of the stopper member in the direction opposite to the direction of insertion (i.e., in the direction opposite to the direction of installation) is impeded.
In accordance with the present invention, there are cases in which a resistance imparting device is provided between the spool and the locking device. The resistance imparting device usually rotates integrally with the spool without imparting rotational resistance to the spool. However, at the time of rapid deceleration of the vehicle, when the rotation of the energy absorbing member in the webbing pull-out direction is locked by the locking device, in the initial stage, the resistance imparting device imparts resistance to the rotation of the spool in the webbing pull-out direction. Accordingly, in the initial stage of the rapid deceleration of the vehicle, energy is absorbed at an FL load, in which are added together both an FL load due to deformation of the energy absorbing member and an FL load due to the rotational resistance which the resistance imparting member imparts to the spool. Thereafter, the state in which the resistance imparting member imparts resistance to the spool is cancelled. Accordingly, after the initial stage of the rapid deceleration of the vehicle, energy is absorbed at the FL load due to the deformation of the energy absorbing member. In this way, in accordance with the present invention, the FL load is set to be two stages. At the initial stage of the rapid deceleration of the vehicle, the energy absorption amount is large, and the amount by which the webbing is pulled out (the amount of movement of the vehicle occupant toward the front of the vehicle) is suppressed. Thereafter, the energy absorption amount is decreased and the load applied to the vehicle occupant is lessened.
In this way, in a webbing retractor having a force limiter mechanism in which the FL load is set to be two stages, as described above, a large load is applied to the spool in the initial stage of the rapid deceleration of the vehicle. Therefore, a load in the separating direction is strongly applied to the stopper member. Accordingly, the present invention, which enables the locking device to be strongly fixed to the spool, is suited to this type of webbing retractor.